In Edward Jenner’s 1796 experiment, cowpox inoculation helped protect people against smallpox.
Jenner noticed that milkmaids who had experienced cowpox appeared less likely to contract smallpox. He tested the idea by inoculating James Phipps with material from a cowpox sore and later exposing him to smallpox material.
Phipps did not develop smallpox, and Jenner published his findings in 1798. By modern standards, the procedure would not meet current research ethics, but it became a landmark in the history of vaccination.
The word vaccine comes from vaccinia, the scientific name associated with cowpox. Jenner’s work did not identify viruses or explain immunity at the molecular level; it demonstrated a practical protective effect that eventually led to global smallpox eradication.